U.S. patent application number 15/565559 was filed with the patent office on 2018-05-03 for method for uplink communication in a lte cellular network.
This patent application is currently assigned to GEMALTO M2M GMBH. The applicant listed for this patent is GEMALTO M2M GMBH. Invention is credited to Volker BREUER, Thomas ULRICH, Lars WEHMEIER.
Application Number | 20180124814 15/565559 |
Document ID | / |
Family ID | 52946402 |
Filed Date | 2018-05-03 |
United States Patent
Application |
20180124814 |
Kind Code |
A1 |
BREUER; Volker ; et
al. |
May 3, 2018 |
METHOD FOR UPLINK COMMUNICATION IN A LTE CELLULAR NETWORK
Abstract
The present invention relates to a method for data transmission
from a wireless device to a base node, the base node is part of a
cellular network and is configured to support frequency division
multiple access method, the bandwidth receivable by the base node
comprising a plurality of subcarriers, the wireless device is
camping on the base node, the method comprises the steps of: --for
the base node, assigning to the wireless device a subcarrier of the
plurality of subcarriers, --transmitting data from the wireless
device to the base node for the period of at least one data service
session using only the assigned subcarrier, whereby using for said
data transmission a first modulation scheme on the assigned
subcarrier different from the modulation scheme used for more than
one of the plurality of the subcarriers by at least one second
wireless device camping on said base node.
Inventors: |
BREUER; Volker; (Boetzow,
DE) ; WEHMEIER; Lars; (Falkensee, DE) ;
ULRICH; Thomas; (Bad Durkheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GEMALTO M2M GMBH |
Munich |
|
DE |
|
|
Assignee: |
GEMALTO M2M GMBH
Munich
DE
|
Family ID: |
52946402 |
Appl. No.: |
15/565559 |
Filed: |
April 12, 2016 |
PCT Filed: |
April 12, 2016 |
PCT NO: |
PCT/EP2016/058037 |
371 Date: |
October 10, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 27/0008 20130101;
H04L 5/0037 20130101; H04W 72/1268 20130101; H04L 27/2636 20130101;
H04W 72/0453 20130101; H04W 4/70 20180201; H04W 72/048 20130101;
H04W 72/042 20130101 |
International
Class: |
H04W 72/12 20060101
H04W072/12; H04W 4/00 20060101 H04W004/00; H04L 27/26 20060101
H04L027/26; H04W 72/04 20060101 H04W072/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2015 |
EP |
15163860.8 |
Claims
1. Method for data transmission from a wireless device to a base
node, the base node is part of a cellular network and is configured
to support frequency division multiple access method, the frequency
bandwidth receivable by the base node comprising a plurality of
subcarriers, the wireless device is camping on the base node, the
method comprises the steps of: for the base node, assigning to the
wireless device a subcarrier of the plurality of subcarriers,
transmitting data from the wireless device to the base node for the
period of at least one data service session using only the assigned
subcarrier, whereby using for said data transmission a first
modulation scheme on the assigned subcarrier different from the
modulation scheme used for more than one of the plurality of the
subcarriers by at least one second wireless device camping on said
base node.
2. Method according to claim 1, wherein the first wireless device
and the second wireless device are assigned to different device
domains of the cellular network.
3. Method according to claim 1, comprising the step for the base
node of indicating to the wireless device the capability of
supporting the indicated first modulation scheme, and subsequently
receiving transmissions from the wireless device using the first
modulation scheme.
4. Method according to claim 1, comprising the step for the base
node of indicating subcarriers reserved for the first modulation
scheme out of the plurality of subcarriers to the wireless
device.
5. Method according to claim 1, wherein the first modulation scheme
is a narrow band transmission scheme, out of the group of:
continuous wave, and Gaussian Minimum Shift Keying.
6. Method according to claim 1, wherein the assigned subcarrier is
an edge subcarrier, characterized in that the subcarrier is
situated at one end of the frequency band supported by the base
node.
7. Method according to claim 1, wherein the assigned subcarrier is
based on frequencies on the flank of the frequency band supported
by the base node, and said subcarrier is only usable for wireless
devices supporting the first modulation scheme.
8. Wireless device configured to camp on a base node, being part of
a cellular network and being configured to support frequency
division multiple access method, and the base node being configured
to receive a frequency bandwidth comprising a plurality of
subcarriers, wherein the wireless device is configured to receive
from the base node a subcarrier from said plurality of subcarriers,
and transmit data to the base node for the period of at least one
data service session using only the assigned subcarrier, wherein
the wireless device is configured to use for said data transmission
a first modulation scheme on the assigned subcarrier different from
the modulation scheme used for more than one of the plurality of
the subcarriers by at least one second wireless device camping on
said base node.
9. Wireless device according to claim 8, wherein the wireless
device is assigned to a different device domain of the cellular
network than the at least one second wireless device.
10. Wireless device according to claim 8, wherein the first
modulation scheme is a narrow band transmission scheme out of the
group of: continuous wave, and Gaussian Minimum Shift Keying.
11. Base node being part of a cellular network, the base node being
configured to support frequency division multiple access method and
further configured to receive a frequency bandwidth comprising a
plurality of subcarriers from at least one wireless device camping
on the base node, wherein the base node is further configured to:
assign to said wireless device a subcarrier of the plurality of
subcarriers, receive data transmission from said wireless device
for the period of on-one data service session using only the
assigned subcarrier, wherein the said data transmission is received
in a first modulation scheme on the assigned subcarrier different
from the modulation scheme used for more than one of the plurality
of the subcarriers by at least one second wireless device camping
on said base node.
12. Base node according to claim 11, wherein the base node is
further configured to indicate to the wireless device the
capability of supporting the indicated first modulation scheme, and
subsequently to receive transmissions from the wireless device
using the first modulation scheme.
13. Base node according to claim 11, wherein the base node is
further configured to indicate subcarriers reserved for the first
modulation scheme out of the plurality of subcarriers to the
wireless device.
14. Base node according to claim 11, wherein the first modulation
scheme is a narrow band transmission scheme, out of the group of:
continuous wave, and Gaussian Minimum Shift Keying.
15. Base node according to claim 11, wherein the assigned
subcarrier is an edge subcarrier, characterized in that the
subcarrier is situated at one end of the frequency band supported
by the base node.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for data
transmission from a wireless device to a base node, in particular
for low capability wireless device in a long term evolution
network.
[0002] The invention also pertains to a wireless device using said
method. The invention further relates to a base node communicating
with said wireless device.
BACKGROUND OF THE INVENTION
[0003] Generally, in the field of wireless communication the
technology of long term evolution (LTE) is being standardized by
the 3GPP as a technology allowing higher bandwidth with reduced
latencies, in particular in order to allowing the introduction of
new services with higher data needs than offered by the available
cellular networks supporting 2G (GSM, GPRS, EDGE) or 3G (UMTS,
HSPA). At the same time there are tendencies of the network
operators to reduce the number of maintained cellular network
standards. At long sight it is expected that at least one of the
legacy cellular networks will be switched off.
[0004] On the other hand the definition of the long term evolution
standard implies that wireless devices supporting the standard--no
matter in what kind of service--need to provide certain
capabilities which require wireless devices with a remarkable
processing power. In particular the need to support a 20 MHz
frequency band in one millisecond requires a significant amount of
hardware resources on the side of the wireless device.
[0005] This situation is of course incompatible with the growing
trend of machine-to-machine (M2M) devices. Those M2M devices are
typically those where machines like vending machines, point of sale
(POS) devices, electricity meters or other sensor devices, or home
security devices regularly communicate via the cellular network
with remote servers, and they are preferably designed for rarely
sending small amounts of data. Those M2M devices are hence low
capability wireless devices. They are usually equipped with a
wireless module incorporating all required components for
conducting all signaling exercises with the cellular network they
are operating in.
[0006] From a cost perspective a low capability wireless device
like the mentioned examples would merely be attractive if a LTE
capable wireless module would be incorporated. At the same time
there are by now already millions of low capability wireless
devices in the field, and if only they would switch to LTE, the
present LTE capable cellular networks (LTE networks) would capacity
wise be overwhelmed with this load. This is the case even if the
low capability wireless devices as such are only rarely sending
data, as a remarkable amount of overhead signaling is required
according to today's standard specification without providing any
payload.
[0007] There is therefore a need for an adaptation of the LTE
standard in order to on the hand support low cost devices, in
particular low capability wireless devices, and on the other hand
to prepare the LTE networks for serving the expected amount of low
capability wireless devices.
[0008] It is by now known that a reduction of the frequency band to
a smaller portion of carriers that need to be supported by the low
capability wireless devices, including the uplink communication,
would reduce the processing resources on side of the wireless
device. By now those approaches did not lead beyond the required
amount of 1.4 MHz corresponding to the basic unit of a resource
element. Moreover there are approaches missing that ease the
processing requirements of a low cost device for uplink
communication beyond the mere supported bandwidth.
[0009] It is therefore a goal of present invention to propose a
solution for an improved communication protocol of LTE capable
wireless device in the uplink direction to a corresponding base
node, which allows remarkable reductions in the processing
resources of the wireless device with low impact on the
architecture of the base node.
SUMMARY OF THE INVENTION
[0010] Therefore it is according to a first aspect of the invention
suggested a method for data transmission from a wireless device to
a base node according to claim 1. It is further suggested according
to a second aspect of the invention a wireless device according to
claim 8. According to a third aspect of the invention it is
proposed a base node according to claim 11.
[0011] It is therefore proposed according to the first aspect of
the invention a method for data transmission from a wireless device
to a base node, the base node is part of a cellular network and is
configured to support frequency division multiple access method,
the bandwidth receivable by the base node comprising a plurality of
subcarriers, the wireless device is camping on base node, the
method comprises the steps of: [0012] for the base node, assigning
to the wireless device a subcarrier of the plurality of
subcarriers, [0013] transmitting data from the wireless device to
the base node for the period of at least one data service session
using only the assigned subcarrier, whereby using for said data
transmission a first modulation scheme on the assigned subcarrier
different from the modulation scheme used for more than one of the
plurality of the subcarriers by at least one second wireless device
camping on said base node.
[0014] The method is based on a base node of a cellular network,
wherein the base node supports frequency division multiple access
method. This is in particular true for base nodes supporting the
LTE wireless standard, the so-called eNodeBs. In LTE uplink
communication is preferably conducted using single carrier
frequency division multiple access, which means that a wireless
device operating with the base node is providing data in the same
frequency range together with other wireless devices, wherein the
wireless device are supposed to transmit data on one or more
assigned subcarriers of the frequency band, as opposed to LTE
downlink where the base node can distribute the transmitted symbols
for one receiving wireless device over the full range of
subcarriers of the supported frequency band.
[0015] A subcarrier represents a 15 kHz section of the frequency
band.
[0016] As part of the uplink data transmission the base node
assigns to the wireless device the respective subcarrier it is
expected to use for the subsequent data transmission.
[0017] This is preferably happening in conjunction with a request
from the wireless device for setting up a data service session.
This is in particular a period where the wireless device is
supposed to transmit data to the base node and/or to transmit to
and receive data from the base node. Such a data service session is
in particular a data connection, a onetime transmission period or
the time the wireless device is camping on the base node. Other
events starting and/or ending a data service session are
nonetheless also covered.
[0018] In response the wireless device is transmitting data on the
assigned subcarrier, that is in the frequency range of 15 kHz by
means of a modulation scheme, which is different from modulation
schemes used by other wireless devices operating with this base
node. The used first modulation scheme is in particular a
narrowband modulation scheme, which is characterized in that it
uses just one subcarrier, hence a single subcarrier modulation
scheme. It is in particular suggested that the first modulation
scheme is a narrow band transmission scheme, out of the group of:
[0019] continuous wave (CW), and [0020] Gaussian Minimum Shift
Keying (GMSK).
[0021] These narrowband transmissions schemes are in particular
those used within GSM capable cellular networks.
[0022] Hence the wireless device makes use of the signaling
structure of SC-FDMA but embeds within the assigned subcarrier a
different modulation scheme as the common modulation schemes used
in LTE, in particular BSPK, QPSK, 16QAM, 64-QAM, which each is a
wideband modulation scheme, in particular a frequency multiplexing
transmission scheme covering at least one resource block,
consisting of 12 subcarriers.
[0023] This leads to the situation that at the wireless device for
transmitting data far less resources are needed: [0024] only one
subcarrier at a time is addressed, [0025] for modulation scheme
less processing power is needed, in particular as no fast fourier
transformation (FFT) resp. inverse fast fourier transformation
(IFFT) needs to be carried out.
[0026] Instead, with a simpler modulation scheme the wireless
device in its transmissions takes advantage of the SC-FDMA
structure, in particular the guard intervals and subcarrier spacing
resp. guard bands separating the subcarriers, in order to assure
that the transmission is not disturbed by other transmitting
wireless devices, but does not need the complexity which is
expected for wireless devices supporting full fledged LTE resp.
SC-FDMA.
[0027] In that sense, the data transmission using the first
modulation scheme is embedded in the SC-FDMA structure.
[0028] According to a further advantageous embodiment the first
wireless device and the second wireless device are assigned to
different device domains of the cellular network.
[0029] With that embodiment it is made use of the definition of
domains within the cellular networks. In particular
machine-type-communication (MTC) devices are preferred to be
handled as a separate domain than mobile handsets. With the concept
of domains--regardless of the specific implementation within the
cellular network--the cellular network has means to handle such
wireless devices differently. This leads to the possibility that
only those wireless devices operating in a first domain, in
particular for MTC devices, are operating according to the
inventive method and using a different modulation scheme for uplink
transmission.
[0030] This is in particular advantageous as MTC devices have
preferably different needs in terms of data transfer rates than
mobile handset. While common fully equipped wireless devices are
targeting a maximum of data transmission rate, the MTC devices have
typically quite opposite requirements. For a wireless device like
an electricity meter the transmission time is secondary. Hence less
effective modulation schemes are appropriate for the
transmission.
[0031] According to another preferred embodiment of the invention
it is suggested a method comprising the step for the base node of
indicating to the wireless device the capability of supporting the
indicated first modulation scheme, and subsequently receiving
transmissions from the wireless device using the envisaged first
modulation scheme.
[0032] With this embodiment the wireless device receives from the
base node the indication, if the base node is capable of supporting
the first modulation scheme.
[0033] The indication is in particular submitted with a broadcast
from the base node to a multitude of wireless devices, in
particular the ones being assigned to the first domain, preferably
the MTC domain. The broadcast is preferably part of the system
information blocks (SIBs) submitted as part of the BCCH. For the
system information it is in particular foreseen to reserve certain
system information to MTC devices only. Hence, the indication that
the first modulation scheme is supported is preferably integrated
in one of the M-SIBs.
[0034] When the wireless device receives this information, in
response the next data transmission will be started using the first
modulation scheme.
[0035] For those wireless devices which are in particular
physically only capable of transmitting data by means of the first
modulation scheme, in particular because not enough resources for
other modulation schemes supported by the base node are available,
said indication from the base node is in particular used as a
suitability criterion. This in particular means, if the wireless
device wants to camp on the base node, and the base node indicates
that it is not supporting the first modulation scheme, the wireless
device needs to find another base node, if available.
[0036] According to another preferred embodiment it is suggested
method comprising the step for the base node of indicating
subcarriers reserved for the first modulation scheme out of the
plurality of subcarriers to the wireless device.
[0037] With this embodiment the base node additionally or
alternatively indicates to the wireless device which subcarrier is
to be used for a data transmission by means of the first modulation
scheme.
[0038] Preferably the previous indication if the base node is
capable of supporting the first modulation scheme is combined with
this indication. This means, if the base node indicates to the
wireless device, which subcarrier is to be used for data
transmission by means of the first modulation scheme, this is
additionally the information for the wireless device, that the base
node supports the first modulation scheme. If no subcarrier is
indicated, the wireless device preferably is looking for another
base node.
[0039] In a further preferred embodiment it is proposed a method
wherein the assigned subcarrier is an edge subcarrier,
characterized in that the subcarrier is situated at one end of the
frequency band supported by the base node.
[0040] In conjunction with the assigned subcarrier it is according
to this embodiment advantageous to reserve--if available--the
subcarriers for the data transmissions by means of the first
modulation scheme at the edges of the frequency range. This reduces
interference with other subcarriers.
[0041] Alternatively or additionally a narrowband RF-filter is
adapted to the single subcarrier which reduces interference with
adjacent subcarriers. This also makes guard band radio spectrum
available for such data transmissions. According to a further
advantageous embodiment it is suggested a method wherein the
assigned subcarriers is based on frequencies on the flank of the
supported frequency band, and said subcarrier is only usable for
wireless devices supporting the first modulation scheme.
[0042] This embodiment moreover proposes that subcarriers are used
that are beyond the frequency range which is allocated for the
dedicated number of subcarriers for a frequency band. Typically the
receiver of the base node is able to receive a larger frequency
bandwidth than it is used for decoding. In particular in the
respective frequency bands a number of subcarriers lower than a
power of 2 are available. As for the fast fourier transformation
(FFT) input values corresponds to a power of 2, the remaining
subcarriers are well equipped for transmitting data in a modulation
scheme, which are not allocated for subcarriers. Hence it is
suggested to assign those subcarriers in this guard band for the
data transmissions according to the first modulation scheme.
[0043] According to the second aspect of the invention it is
proposed a wireless device configured to camp on a base node, being
part of a cellular network and being configured to support
frequency division multiple access method, and the base node being
configured to receive a bandwidth comprising a plurality of
subcarriers, wherein the wireless device is configured to [0044]
receive from the base node a subcarrier from said plurality of
subcarriers, and [0045] transmit data to the base node for the
period of at least one data service session using only the assigned
subcarriers, [0046] wherein the wireless device is configured to
use for said data transmission a first modulation scheme on the
assigned subcarrier different from the modulation scheme used for
more than one of the plurality of the subcarriers by at least one
second wireless device camping on said base.
[0047] The wireless device in particular comprises at least a
processing unit, a memory unit and a wireless transceiver. The
wireless device is able to support the first modulation scheme, in
particular it is only capable for data transmissions to use this
first modulation scheme. In particular the wireless device
comprises a wireless transceiver, including a RF-unit, wherein the
transceiver is capable to transmit data in a frequency range
sufficient to address one subcarrier. This is in particular
advantageous as it saves hardware resources for the affected low
cost wireless devices.
[0048] The second aspect shares the advantages of the first aspect
of the invention.
[0049] According to the third aspect of the invention it is
proposed a base node being part of a cellular network, the base
node being configured to support frequency division multiple access
method and further configured to receive a bandwidth comprising a
plurality of subcarriers from at least one wireless device camping
on the base node, wherein the base node is further configured to:
[0050] assign to said wireless device a subcarrier of the plurality
of subcarriers [0051] receive data transmission from wireless
device for the period of on data service session using only the
assigned subcarrier, wherein the said data transmission is received
in a first modulation scheme on the assigned subcarrier different
from the modulation scheme used for more than one of the plurality
of the subcarriers by at least one second wireless device camping
on said base node.
[0052] Generally this aspect shares the advantages of the first
aspect of the invention.
[0053] Additionally it is advantageous that existing base node
implementations, in particular eNodeBs used in today's LTE
implementations are from the physical preconditions already suited
for being configured according to the invention. In particular the
RF-part requires no changes as the same frequency bands are
expected to be received. Hence only a software update would be
sufficient to adapt the uplink resource scheduler and preferably
the downlink transmission, in particular in a broadcast of system
information, indicating the capability of supporting the first
modulation scheme.
[0054] As it is shown this invention advantageously solves the
depicted problem and allows wireless devices with low resources to
operate within LTE networks according to their data transmission
needs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] The following description and the annexed drawings set forth
in detail certain illustrative aspects and are indicative of but a
few of the various ways in which the principles of the embodiments
may be employed. Characteristics and advantages of the present
invention will appear when reading the following description and
annexed drawings of advantageous embodiments given as illustrative
but not restrictive examples.
[0056] FIG. 1 represents a block diagram of operating steps from
transmitting user equipment and receiving base node according to
the prior art
[0057] FIG. 2 represents a block diagram of operating steps from
transmitting user equipment and receiving base node according to a
preferred embodiment of the invention
[0058] FIG. 3 shows the frequency time diagram in the uplink
according to a preferred embodiment of the invention
[0059] FIG. 4 shows used and unused frequency band and the use of
guard bands as part of a preferred embodiment of the invention.
[0060] FIG. 1 schematically shows the operating step of wireless
device respectively a user equipment (UE) and a base node (BS)
being part of a LTE network according to the prior art for an
uplink transmission according to single carrier frequency division
multiple access. The process is shown as a processing queue through
the UE to the BS.
[0061] In the present example a couple of payload data are put into
the process, e.g. as part of a data service session by one UE. The
following steps are generally executed by the UE within the
protocol stack and in conjunction with the radio frequency unit
(RF).
[0062] At first the payload data are modulated using the common LTE
modulation schemes GPSK, 16-QAM or 64-QAM, depending upon the
amount of data and the configured scheme with the BS. Then the
modulated data are parallelized that is in one time parts of the
modulated data are separated on multiple paths.
[0063] These paths in the time-domain are then converted by means
of the Forward Fast Fourier Transformation (FFT) in the frequency
domain. Based on the data in the frequency domain a mapping on
separate subcarriers is possible. As subcarriers each cover 1.4
kHz, one or more subcarriers are depending upon the resources
assigned from the base node usable for the data transmission of the
specific UE. Typically the mapping is in particular done on
resource blocks, which are in fact composed of 12 subcarriers
itself.
[0064] The mapping to the subcarriers then needs to be transformed
for analogue serial transmission on the lower layers. For that
first an inverse FFT back in the time domain is carried out, and
the result can then be used for serialization.
[0065] Specific for LTE is the addition of cyclic prefixes. That
means that the serialized transmission on the frequency of the
specific subcarrier is enhanced by so-called guard periods, before
the analogue transmission over the air interface S1 to the base
node is executed.
[0066] In the BS the reverse operation needs to be carried out,
whereby data from different UEs are expected to be received in the
respective frequency range which needs to be sorted out.
[0067] First the exact reverse operations to the last operations in
the UE are executed: reception of analogue transmitted data over
the air interface, then removal of guard periods as part of the
cyclic prefix handling, parallelization of data and forward FFT
from the time domain in the frequency domain.
[0068] In the subcarrier selection step, the data transmission from
different UEs, which each got assigned their subcarriers for data
transmission, are separated by transmitting UE. For the subcarriers
for the shown UE in this example the leftmost four subcarriers are
reserved and handled accordingly. Like in OFDMA then the steps of
equalization and channel estimation are done, which refers to the
usage of received reference symbols in the data transmissions with
respect to amplitude changes and phase shifts on the incoming
transmissions.
[0069] Finally the data on the subcarriers are transformed in the
time domain by means of the inverse FFT, and are serialized in the
following. At the end a demodulation reverting the modulation from
the beginning needs to be carried out in order to receive the
originally transmitted payload. The demodulation needs to use the
same modulation scheme, only reverted, as it was done at the
modulation step in the UE.
[0070] In contrast FIG. 2 shows the same procedure for an
exemplifying embodiment of the invention. As it can be seen the
simplification is mainly affecting the UE, which was the goal of
the invention.
[0071] It starts in step US1 on the UE side with the payload which
is to be transmitted from the UE to the BS. Actually the
transmission from one of a plurality of UEs is shown, here
indicated as UE(1).
[0072] In the next step the modulation US2 is carried out which
uses a single subcarrier narrowband modulation scheme, in
particular GMSK or CW. These modulated data only needs to be
shifted to the respective subcarrier frequency. The frequency
refers to the subcarrier assigned from the BS for data transmission
in an earlier step, in particular at registration, setup of data
connection or a different start of a data service session.
[0073] As an adaptation to comply to the LTE protocol structure the
handling is added in step US3 as well, that is guard periods are
added in the modulated data stream, which is nothing more than
inserting quiet phases within constant time periods.
[0074] Finally the resulting output is transmitted in step US4 via
the analogue RF transmitter on the air interface S1.
[0075] As it can be seen neither serialisation/parallelisation
steps nor forward or inverse FFTs are used for the data
transmission according to the invention from the UE to the BS. If
the analogue transmitter is only capable of supporting the
narrowband modulation scheme, even the RF-transmitter has only the
range sufficient to transmit one subcarrier.
[0076] On the BS side practically the same steps BS1 to BS10 are
executed as according to the prior art. The subcarrier selection in
BS5 leads to as many subcarriers as UEs transmitting data with the
narrowband modulation scheme. Here is it indicated with two arrows,
that two subcarrier, in particular the edge subcarriers of the
respective frequency range, were reserved, at least timewise for
such MTC-UEs using the narrowband modulation scheme, with results
in separate payloads BS10 from the different UE(1), UE(n). So for
each of the transmitting UE(n) the next steps BS6 to BS10 are
carried out. Only the demodulation step BS9 differs from the
demodulation according to the prior art, as here the respective
demodulation scheme needs to be chosen.
[0077] This processing queue on the BS side shows that no material
changes are necessary on the base nodes supporting the inventive
method. This is in particular true for the hardware parts, in
particular the receiver, but also the general process is not
materially changed which therefore only needs slight software
modifications in order to support the inventive method.
[0078] FIG. 3 shows in a diagram over frequency and time the
structure of the support frequency division multiple access method
with the enhancement of an embodiment of the proposed invention.
The diagram is over frequency 1 and time 2, and shows the signaling
of the subcarriers 3 in a respective frequency bandwidth 4.
[0079] On the frequency axe 1 it is shown the amplitudes 8 of the
signals transmitted on neighboring subcarriers 3. This shows the
OFDMA typical distribution of the spacing of subcarriers by 15 kHz
of the maximum of amplitudes 8, with an overlapping of the
amplitudes, which nevertheless allows sufficient signaling quality
without additional guard frequency. This design is one of the bases
for achieving higher transmission rates with LTE rather than in
previous technology standards.
[0080] Further each single OFDM symbol 6 is spaced by a cyclic
guard period 5 which leads to a synchronization of the whole data
transmissions. This structure is common to the subcarriers' time
domain 9.
[0081] This concept generally affects the uplink and downlink
transmission.
[0082] According to the preferred embodiment of the invention for a
specific frequency 4.1, representing one specific subcarrier 3,
instead of the SD-FDMA signaling another narrowband modulation
scheme is embedded in the frequency bandwidth. In the specific
embodiment this is shown as an edge subcarrier, which is
advantageous as part of a specific embodiment of the invention. The
transmission 7 on this subcarrier in the specific modulation scheme
lasts along the time axis and also includes guard periods 5.
[0083] By means of taking advantage of the common amplitude
structure of the subcarriers, interferences are omitted on the
frequency of a specific subcarrier. With the narrowband structure
of the modulation scheme no additional interferences are
introduced, hence this modulation scheme can be embedded in the
rest of the subcarrier's amplitude structure. This is due to the
fact that an increase of capacity requirements for data
transmissions is only requested in the time domain, not in the
frequency domain. That means, that additional data transmissions
simply take longer, which is supposed to be non-critical for the
envisaged UEs. Additionally another subcarrier, preferably adjacent
to the first subcarrier, is foreseen to be used by a UE, when more
capacity is required and the resources are available both at the UE
and the air interface.
[0084] FIG. 4 shows as part of a further preferred embodiment of
the invention the frequency band between a UE and a BS according to
the LTE standard. It is exemplarily shown the frequency band of 15
MHz. For this frequency band it is according to the LTE standard
foreseen an amount of 900 subcarriers, which covers a total of 13.5
MHz. On the edges of the frequency band a guard band 14 is
added.
[0085] Further the FFT is executed best when a number of calculated
data-points, in this case subcarriers, equals a power of 2. For the
900 MHz band this would equal to 1024 subcarriers. Hence, although
only 900 subcarriers are declared, each BS is able to receive at
least the 1024 subcarriers and carry out the FFT on the received
subcarriers.
[0086] This leaves to a flank 12 additionally to the supported
frequency range actually readable by the BS.
[0087] A common UE 11b operating according to the known LTE
standard is using the area 10 for data submissions according to the
assigned subcarrier resp. resource blocks distributed over the
frequency of 13.5 MHz.
[0088] A low cost UE 11a which is capable to support the inventive
method is in particular only configured to transmit data in a
smaller range at a time. Over the full area of the frequency band,
indicated by dashed lines, the UE is able to support a designated
transmissions frequency, that it the subcarrier for data
transmissions according to the first modulation scheme.
[0089] On the flank 12 of the readable frequency range the UE 11a
hence is able to transmit data on a subcarrier 15 outside of the
frequency area 10, preferably outside of the guard band 14.
[0090] This option is in particular advantageous as by this the
frequency of other high performance wireless devices is not
allocated. In particular as certain low cost UEs might due to the
low transmission rate of the used narrowband modulation scheme take
longer time for relatively low data amounts, the subcarriers
allocated for low cost UEs would be blocked for a remarkable while.
With dedicated subcarriers outside of the addressable frequency
band of common LTE devices, here no resource collision in the air
interface is happening. Further no hardware modifications on the BS
side are necessary, as the used frequency band is still inside the
frequency range which must be readable for the BS anyhow.
[0091] In the above detailed description, reference is made to the
accompanying drawings that show, by way of illustration, specific
embodiments in which the invention may be practiced. These
embodiments are described in sufficient detail to enable those
skilled in the art to practice the invention. It is to be
understood that the various embodiments of the invention, although
different, are not necessarily mutually exclusive. For example, a
particular feature, structure, or characteristic described herein
in connection with one embodiment may be implemented within other
embodiments without departing from the scope of the invention. In
addition, it is to be understood that the location or arrangement
of individual elements within each disclosed embodiment may be
modified without departing from the scope of the invention. The
above detailed description is, therefore, not to be taken in a
limiting sense, and the scope of the present invention is defined
only by the appended claims, appropriately interpreted, along with
the full range of equivalents to which the claims are entitled.
* * * * *